The invention relates to a tool for hot-forming and/or press-hardening of a sheet-metal material. The invention furthermore relates to a method for the production of a cooling device for such a tool.
Hot-forming is generally understood to mean forming of a sheet-metal material above its recrystallization temperature. Press-hardening or mold-hardening is understood to mean forming of a previously heated sheet-metal material with simultaneous cooling (within a few seconds), with an increase in strength being brought about as a result, along with shaping of the sheet-metal material. Different method variants for hot-forming and press-hardening (for example direct and indirect press-hardening) are known from the state of the art.
Hot-forming tools and press-hardening tools are typically configured with integrated cooling devices, in order to be able to actively cool the active tool surfaces that come into direct contact with the heated sheet-metal material, and in order to be able to conduct the heat energy introduced into the tool by means of the heated sheet-metal material away from the tool in targeted manner. These cooling devices are usually cooling bores or cooling channels disposed in the tool, through which a cooling medium (particularly on the basis of water) flows, in order to thereby bring about active cooling of the active tool surfaces. With regard to the state of the art, reference is made to DE 10 2007 003 745 A1.
A tool for press-hardening of a sheet-metal material is known from DE 10 2007 040 013 A1, in which a cooling device is composed of a cooling insert having cooling channels worked into it and a lid (or shell) set onto this cooling insert, on which lid an active tool surface is also configured.
The invention is based on the task of indicating a tool for hot-forming and/or press-hardening of a sheet-metal material, having at least one cooling device integrated into the tool, which tool can be produced in simple and cost-advantageous manner.
This task is accomplished by means of a tool according to the invention. The solution for the task also extends to cover a method for the production of a cooling device for this tool. Preferred further developments and embodiments are evident, analogously for both objects of the invention, from the dependent claims and from the following explanations.
The tool according to the invention has multiple cooling devices that are integrated into the tool and through which a coolant can flow, but at least one such cooling device, in order to thereby be able to actively cool the active tool surfaces that come into direct contact with the sheet-metal material, at least in certain regions, in other words to be able to conduct heat away out of the tool. It is provided that at least one cooling device of the tool according to the invention comprises a shell element having an active tool surface or an active tool surface section configured on it, where this shell element has multiple separate cooling chambers on a rear side, facing away from this active tool surface, through which a coolant can flow, and at least one flow guide element for the coolant is disposed in each of these cooling chambers.
A defined flow through the cooling chamber, in each instance, is achieved with the at least one flow guide element. In other words, the at least one flow guide element serves to control a coolant volume stream through the cooling chamber. The flow guide elements, in each instance, are inserted into the related cooling chambers in the shell element and attached. The cooling chambers of the shell element are typically configured with different spatial contours or shaping. The flow guide elements disposed in the cooling chambers therefore have a different configuration or shaping. In particular, it is provided that individual adaptation of a cooling chamber and the flow guide elements inserted into it takes place merely by means of finishing or reworking these flow guide elements, where this working can be undertaken at any time (in other words even after the tool is already in operation). The flow guide elements can be formed from a material that can be worked in particularly simple manner, as will still be explained in greater detail below. Complicated chip-removing or cutting work, as is required for the tools known from the state of the art and their cooling devices, is therefore eliminated to a great extent. With the idea according to the invention, the production effort and costs (particularly also the material costs) are significantly reduced as compared with the concepts known from the state of the art, without any restriction in the geometric shaping possibilities for the sheet-metal material to be formed. Furthermore, time savings in the production process also occur. Repair and maintenance processes are also shorter and more cost-advantageous.
The shell element preferably has multiple cooling chambers that are configured the same and/or differently. However, the shell element can also have only a single cooling chamber. The cooling chambers of the shell element are preferably configured as separate cooling chambers through which flow can take place, in other words every cooling chamber is separately supplied with cooling medium that flows through it. Preferably, it is provided that two adjacent cooling chambers are divided by a support rib disposed between them. The support rib can also serve for supporting the shell element on a basic tool body (or the like), on which the shell element is attached. As a result, the shell stability and the pressure strength are significantly improved.
Particularly preferably, it is provided that a flow guide element configured as a one-piece body (also referred to as a flow guide body hereinafter) is provided or disposed in each cooling chamber of the shell element. Each body or flow guide body is adapted, in terms of its shaping, to the related cooling chamber in which it is positioned or inserted. Preferably, it is provided that a gap (also referred to as a flow gap hereinafter) is present or exists between the outer surface of the flow guide body and the inner wall of the cooling chamber (cooling chamber wall), at least in certain sections, through which gap the coolant can flow in defined manner, or through which gap a coolant volume stream can be guided, where the control of the coolant volume stream takes place more or less by means of the surface of the flow guide body. In order to set the flow conditions, the flow guide body can be provided, at least in certain regions, with a surface and/or coating that reduces or increases the fluid friction. Furthermore, such a flow guide body has no supporting or stabilizing function for the shell element, but rather serves only for bringing about a defined coolant volume stream in the cooling chamber in question. Such a flow guide body can furthermore also be configured or composed of multiple body elements. Furthermore, the flow through a cooling chamber can be influenced in targeted manner, using what are called turbulence promoters, in order to set a turbulent or laminar flow, for example.
Particularly preferably, it is provided that the flow guide body disposed within a cooling chamber can have the coolant flow around it all over, thereby preventing overheating of the flow guide body, among other things. In this case, a surface offset exists between the surface of the flow guide body and the cooling chamber wall. The surface offset can be uniform or constant. Preferably, however, it is provided that the surface offset is locally different.
Instead of such a flow guide body, a plurality of flow fins can also be provided, which are disposed in a cooling chamber. This will be explained in greater detail below, in connection with the figures.
Preferably, the flow guide body consists of a plastic material or of a composite plastic material (this is also meant to include resin materials and materials or composite materials similar to resins). Particularly preferably, the flow guide body is a cast plastic body. Alternatively, the flow guide body can also consist of an aluminum material or of a similar metal material. Plastic materials and aluminum materials are characterized by low weight and by easy processability and workability, and thereby the flow guide body can easily be individually adapted to the related cooling chamber.
The flow guide bodies disposed in different cooling chambers of a shell element can be connected or combined to form a structural unit, using at least one holder rail (or holder strip or the like). Attachment and position fixation of the flow guide bodies within the cooling chambers can also take place by way of the holder rail.
The shell element can be a cast metal part, where the cooling chambers are already present in the casting blank, and the cooling chamber walls remain unworked, to a great extent (in other words particularly without chip-removing reworking). In other words, the shell element, made available as a cast metal part, has unworked cooling chambers, to a great extent. However, the cooling chamber walls can be provided with a coating, for example with a plastic coating that is sprayed on. A shell element configured in this manner proves to be relatively cost-advantageous. Alternatively, the shell element can also be configured as a milled metal part, for example. In particular, it is a one-piece cast metal part or milled metal part (in other words produced in one piece).
The tool according to the invention can have a lower tool part and an upper tool part (movable relative to one another), where opposite cooling devices according to the above explanations are present both in the lower tool part and in the upper tool part, the cooling chambers of which device are, however, disposed offset relative to one another. In this way, heat stagnation points or heat nests can be avoided, and the cooling output as a whole is optimized.
The solution of the task also extends to cover a method for the production of a cooling device for use in a tool according to the invention. This production method comprises at least the following production or method steps:                production of the shell element (with the cooling chambers) as a milled metal part or as a cast metal part;        casting of a liquid plastic or metal material into the cooling chambers of the shell element, which are essentially unworked, and allowing the cast plastic or metal material to harden or cool (hardening typically takes place within a relatively short time; if necessary, the cooling chambers can be coated with a parting agent or lined with a film); and        unmolding of the flow guide bodies formed by hardening or cooling from the cooling chambers, and, if necessary, individual finishing of these flow guide bodies for adaptation to the respective cooling chamber and, in particular, for setting a specifically adapted flow gap.        
Furthermore, the above and following explanations with regard to the tool according to the invention apply analogously for this production method, and vice versa.
The invention will be explained in greater detail below, using the schematic figures as examples, in non-restrictive manner. The characteristics shown in the figures and/or explained below can be general characteristics of the invention, independent of concrete combinations of characteristics.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.